Development of nano-sensors for eucalyptol detection: A tool for extreme wildfire surveillance

Extreme wildfires have devastating impacts, causing loss of human life and severely affecting ecosystem biodiversity. Despite their significance, the mechanisms behind these events remain insufficiently understood. Recent models suggest that volatile organic compounds (VOCs) emitted by plants in Mediterranean ecosystems, such as eucalyptol, can contribute to the formation of highly flammable atmospheric conditions, acting as ignition sources and promoting sudden shifts in fire behavior. Therefore, the development of reliable monitoring systems capable of detecting these compounds is essential for early fire risk assessment and prevention. In this study, an electronic nose (e-nose) was developed to detect and quantify eucalyptol concentrations ranging from 205 to 999 ppm v . Thin films of metal oxides (ZnO, TiO₂, and ZnO/TiO₂) and organic multilayers composed of poly(allylamine hydrochloride) (PAH), polyethyleneimine (PEI), and graphene oxide (GO) were deposited onto ceramic substrates with gold interdigitated electrodes using magnetron sputtering and the layer-by-layer (LbL) technique, respectively. Impedance spectroscopy demonstrated that all developed sensors could reliably distinguish among different eucalyptol concentrations based on their electrical responses. The best-performing sensors, namely ZnO (250 W, 80% O₂), TiO₂ (500 W, 20% O₂ and 1000 W, 50% O₂), (PAH/GO)₅, (PAH/GO)₁₀, and (PEI/GO)₁₀, were assembled into an optimized sensor array. Principal Component Analysis (PCA) revealed a clear linear trend between the first principal component (PC1) and eucalyptol concentration. The resulting e-nose achieved a sensitivity of 0.051 ± 0.002 per decade of eucalyptol and a resolution of 0.041 ppm v , demonstrating a high potential for the detection of eucalyptol and similar VOCs involved in wildfire dynamics. • Wildfires threaten lives and ecosystems; VOCs may fuel extreme fire behavior. • Eucalyptol from plants can create highly flammable air in Mediterranean areas. • A new e-nose capable of detecting eucalyptol levels down to 200 ppmv is proposed. • Metal oxides and organic films were used as sensing thin film layers. • The e-nose showed a clear VOC detection trend with a 0.041 ppmv resolution.